(sports, snowboarding, skiing) Clipping of 900. (900° spin)

plural of 9/11

(climbing) A technical climbing technique used in ice climbing to gain a respite and lessen slack and distance from the undersurface/ceiling which one is climbing underneath, which appears like a number "9" in shape, with one arm anchoring the climber to the surface while hanging upside-down, and one leg wrapped around that arm, forming a figurative "9" in shape.

(astronomy) A theoretical ninth planet in the Solar system, the gravitational effects of which would explain the improbable orbital configuration of a group of trans-Neptunian objects that orbit mostly beyond the Kuiper belt.

(psychology) The 1977 revision of the International Classification of Diseases, published by WHO.

plural of 9-to-5

A volleyball game with nine players per side and a larger than normal court.

(music) A meter of nine quavers per measure.

(US, taxation) A form to declare that someone is a U.S. tax payer.

Alternative spelling of nine-tenths